How online games are solving uncomputable problems

ARISTIDES is a typical 13-year-old boy. He plays basketball after school, is learning the clarinet, and in the evening sits in front of his computer playing games. There is one game that he is especially keen on, however, which marks him out from his peers. Every day he logs on to www.fold.it, where, under the nickname “Cheese”, he plays a game that involves twisting, pulling and wiggling a 3D structure that looks a bit like a tree’s root system. He manipulates different lengths of these snaking green tubes until they fit into the smallest volume possible. It may sound like a rather bizarre game – a distant 3D relative of Tetris, perhaps – but it is in fact a brilliant disguise for one of the toughest conundrums facing biologists today&colon; how do proteins fold?

The structures Aristides plays with are computer representations of real proteins such as collagen. Without understanding the first thing about molecular biology, he is contributing to one of the knottiest problems of modern science. “Predicting exactly how a long protein chain curls up as compactly as possible, amongst all the myriad possibilities, is a very hard problem to solve with computers,” says David Baker at the University of Washington in Seattle, who invented the game.

As the length of a protein chain increases, the number of possible ways it can be folded increases exponentially. Even for the simplest chains, it would take a typical desktop computer several centuries to predict the optimum way a protein would fold. Yet with the help of 60,000 amateur …